docs: def host_is_trusted(hostname, trusted_list):
      """Checks if a host is trusted against a list.  This also takes care
      of port normalization.
  
      .. versionadded:: 0.9
  
      :param hostname: the hostname to check
      :param trusted_list: a list of hostnames to check against.  If a
                           hostname starts with a dot it will match against
                           all subdomains as well.
      """
      if not hostname:
          return False
  
      if isinstance(trusted_list, string_types):
          trusted_list = [trusted_list]
  
      def _normalize(hostname):
          if ':' in hostname:
              hostname = hostname.rsplit(':', 1)[0]
          return _encode_idna(hostname)
  
      hostname = _normalize(hostname)
      for ref in trusted_list:
          if ref.startswith('.'):
              ref = ref[1:]
              suffix_match = True
          else:
              suffix_match = False
          ref = _normalize(ref)
          if ref == hostname:
              return True
          if suffix_match and hostname.endswith('.' + ref):
              return True
      return False